Method of inhibiting foam in steam generation



Patented Jan. 20, 1953 METHOD OF 'INHIBITING FOAM IN STEAM GENERATION Arthur L..Jacoby, Western Springs, 111., assignor to National Aluminate Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application May 29, 1948, Serial No. 30,196

9 Claims. 1 The present invention relates to improved a-ntifoaming compositions which are added .to water that is :subj ected to boiling, as .in .the boilers of locomotives, stationary steam generators,

evaporators, and in other instances where the boiling of water occurs, especially .under superatmospheric temperature and pressure conditions, whereby the tendency of the .water therein to foam is preventedor reducedand the boiling characteristics of the water ,so improved that priming of the steam-generator and carryoverof boiler water with the steam therefrom is prevented.

It is well known that .inethe-operationof steam boilers, such as in railroad locomotives, ,in electric power plants and the like, or inother boiling operations where steam is :formed, as forexample in evaporators, that the water =therein, ev en though initially it shows little tendency to-foam, will, when the amount .of .total .dissolved ,solids approaches a relatively high concentration due to the production of steam, develop a .very decided tendency to foam. This foamin of the water in a boiler'producing steam-is characterized not only by an accumulation -.of relatively stable frothor foam .on the surfacepf the boiler water but also by the =formation at the heat transfer surfaces in the boiler of extremely small .steam bubbles. These minute bubbles showalmost ;no tendency to coalesce and the result is that the entire volume of water inthe'steam generator is lifted in the .form .of so=called flight water, which is actually .an intimate mixture .of .boiler water and tiny steam bubbles. when this occurs, considerable .quantities .of boiler water are physically carried .out of the boilers or empty.- rators with the steam, thereby introducing solid matter into the steam lines and into the even.- tual condensate. Such carryover ,has many .disadvantages because it tends to contaminate and restrict the steam lines, to plug or corrode the valves, to deposit on turbine .blades, .to plug and cause burning out .of superheater tubes, and under serious conditions may even impair the cylinders and piston rods -.of steam engines .or otherwise render the steam unfit for use. The carryover is frequently due in part, at least, .to priming, or What may be described as surging or boiling over .of the water.

Attempts have been .made in the past to con.- trol foaming and priming by controlling the dissolved solids content of the water as by ex? cessive blow-down .of .the .boilers, that is, the removal, either continuously or periodically, of a portion of the boiler watericontaining the undesired excess solids. Also, it has been common to ,add materials for the purpose of .abating the foam as by the injection of such materials as castor oil, tallow, and the like. While these fatty materials, notably castor oil, have some small degree of efiiciency, they are, .on the other hand, quite deficient inthat they introduce new difficulties which, in some instances, .are worse than the conditions they are intended to cure. In the first place, these fatty materials or glycerides are very unstable under severe hydrolytic conditions encountered in steam generation, particularly under the conditions of superatmospheric pressure, the corresponding high temperatures and the alkalinity of the boiler water. The resultant decomposition .products whichremain in the'boiler tend to increase the foaming tendencies of the boiler water and to accumulate in such a way as to give a fcompounddirty boiler, necessitating frequent washing. Furthermore, in many instances certain of the decomposition products thus produced, or sometimes .even the materials themselves, have a definite volatility with steam and will, therefore, steam-distil out of the steam generators, thus appearing in the steam and in the eventual condensate. This, of course, is also undesirable. Additionally, such types of antifoaming agents usually are of such a'low order of efliciencythat they have to be employed in relatively large quantities, adding not only to the expense but also to the inconvenience of operating the steam generators; and since they are so unstable their eirectiveness is of short duration, necessitating the continual charging into the boilers .or other steam generators of relatively large amounts of these older antifoaming agents.

The most noteworthy advance over the use of the fatty glycerides described above was the discovery and development .of certain high molecular weight substituted polyamides, which antifoaming compounds overcame many of the disadvantages of the former, especially in that they were highly eflicientat lower dosage levels and much more resistant to decomposition, so that their effective life was relatively greater.

One of the objects of this invention is to provide a new and improved process for preventing the foamin and priming of steam generators, thus improving the quality of the steam produced thereby.

Another object is to provide new and improved compositions for adding to the water in a steam generator to prevent or reduce its tenden y to f am .Another obiectis toprovide antifoaming com- 3 positions which are effective to prevent foaming when used in very low dosages.

A further object is to provide highly effective antifoam compositions which are readily and easily dispersible when added to the feed water entering a steam generator.

Another object of this invention is to provide antifoam compositions in which the active efiective ingredients are readily soluble in water at relatively low temperatures (e. g. '75 degrees F.), but decrease in solubility when the water is heated to relatively high temperatures such as are employed in the generation of steam under superatmospheric pressures and the corresponding temperatures.

Still another object of the invention is to provide a process of generating steam and new and improved antifoam compositions therefor wherein the period of effectiveness of the antifoam composition is greatly prolonged as compared to the period of efiectiveness of other antifoam compositions presently known in the art.

Still another object of the invention is to provide a new and improved process of inhibiting foaming during steam generation which permits operations at higher dissolved solids contents than has heretofore been considered possible.

An additional object is to provide new and useful antifoaming compositions of an extremely high order of resistance to decomposition under the conditions prevailin in steam generation. Other objects will appear hereinafter.

In accordance with this invention, it has now been discovered that there is a series of compounds, which may be broadly designated as high molecular weight diethers of polyoxyalkylene glycols, that are very efiective When used as antifoaming and antipriming agents in steam generators. These polyethers possess several important advantages over formerly known antifoam compositions. They are all much more effective than any of the fatty glycerides, and many are more effective than any hitherto known materials. Furthermore, they are much more stable to decomposition under conditions of use than any of the glycerides or polyamides, thus giving them a greatly prolonged period of effectiveness in preventing foaming. In general, they are more readily dispersed in the water being fed to the steam generator than are older materials, and a further advantage offered by many of these polyethers is that they are liquids or very low-melting waxy materials which are readily soluble at ordinary temperatures.

The preferred polyethers employed in the practice of this invention may be represented by the structural formula wherein R and R are alkyl radicals which may be alike or different, n is 2 or 3 or may have both values, and x is an integer of approximately 6 or larger. Such compounds are thus seen to include dialkyl ethers of polyoxyalkylene glycols including polyoxyethylene glycols, polyoxypropylene glycols and polyoxyalkylene glycols in which the alkylene groups include both ethylene and propylene in any proportion and in a random or irregular sequence, with respect to each other, in the polyoxyalkylene chain.

In order that these diethers of polyoxyalkylene glycols possess the property of efficiently preventing the foaming and priming of steam generators, they should be of relatively high molecular weight, and meet other limiting requirements as more fully set forth hereinafter.

For convenience in describing the structural requirements, the polyethers of this invention will be discussed under four preferred separate classifications.

First, we may consider the class comprising the dialkyl ethers of polyoxyethylene glycols, wherein the terminal alkyl groups are of substantially the same size. For the best results with such compounds in the practice of this invention, each terminal alkyl group should contain at least about 12 carbon atoms and the molecular weight of the whole compound should be greater than about 600, and preferably fall within the approximate range of 700 to 800.

Second, we may consider the dialkyl ethers of polyoxypropylene glycols, wherein the terminal alkyl groups are of substantially the same size. For the best results in the practice of this invention, such compounds should possess a molecular weight greater than about 500, and each terminal alkyl group should contain at least about 8 carbon atoms.

A third group includes dialkyl ethers wherein both ethylene and propylene groups occur in the polyoxyalkylene chain and wherein the terminal alkyl groups are of substantially the same size. For the best results with such compounds in the practice of this invention each terminal alkyl group should contain at least 8 to 12 carbon atoms and the molecular weight of the polyether should be greater than about 600.

The fourth classification includes dialkyl ethers of the above described polyoxyalkylene glycols wherein the two terminal alkyl groups differ widely in number of carbon atoms. For the best results with compounds of this description in the practice of the present invention, it is necessary that one terminal alkyl group contain at least about 12 to 16 carbon atoms while the other may contain only one to six carbons, and that the total molecular weight of the compound be at least about 1500.

The foam inhibiting compounds employed for the purpose of the invention may also be described as being non-ionic in that they do not contain ionizable groups such as carboxy or sulfonic groups.

Althou h, as will be described more fully hereinafter. the polyethers em loyed in accordance with this invention may be prepared by a variety of synthetic routes. and from a variety of reactants, the groups attached to the terminal ether oxygens may be considered as derived from a monohydroxy alcohol. Suitable alcohols are the simple alkanols such as methanol. ethanol, propanol, the butanols, up to higher members such as lauryl. cetyl and octadecyl: alicyclic alcohols, e. g. cyclohexanol; and aralkyl alcohols, e. g., benzylalcohol.

Specific examples of diethers of polvoxyalkylene glycols suitable for the practice of this invention include (1) the dicetyl ether of a olyoxyethylene glycol having an average molecular weight of approximately 300, giving an approximate molecular weight for the compound of 750; (2) the dicetyl ether of a polyoxyethylene glycol having an average molecular weight of approximately 400, giving an approximate molecular weight for the compound of 850; (3) the dilauryl ether of a polyoxyethylene glycol having an average molecular weight of a proximately 400, giving an approximate molecular weight for the compound of 735; (4) the dioctyl ether of a polyoxypropylene glycol of average molecular weight 1200, giving an approximate molecular weight for the compound .of 11425; (5.) dilauryl ether of a polyoxypropylene glycol of average molecular weight 1200, giving an approxima e molecular weight ,for the compound of 1535; (6) the dicetyl ether of apolyoxypropylene glycol of average molecular weight 750, giving an approximate molecular weight for the compound of 1,200; (7) the dialkyl ether of a polyoxypropylene glycol of average molecular weight 1350, wherein one terminal alkyl group is butyl and the other terminal alkyl group is lauryl, the compound having an approximate molecular weight of 1575; and (8) the dialkyl ether of a polyoxyalkylene glycol of average molecular weight950 wherein the ratio of ethylene oxide to propylene oxide in the polyoxyalkylene chain is approximately 1:1, and wherein one terminal alkyl group is butyl and the other terminal alkylg-roup is cetyl, the compound having an approximate molecular weight of '1230.

The compounds of this invention may 'be prepared in several'ways as willbe readily apparent to one skilled in the art. For example, the symmetrical diethers of the polyoxyalkylene glycols may be prepared by reacting two molecular proportions :of the desired alkyl halide with one molecular proportion-ofthe disodium salt of the polyoxyalkylene glycol, according to the following equation: 2RX+NaO(CnH2nO) INa RO (CnHZnO) 2R+2NZX where R is alkyl, 'X ishalogen, e. g., chlorine or bromin n is 2 or .3 or m y both, ands is a whol number of approximately .6 or. larger.

B starting with the dihalide derivative of the polyoxyalkylene glycol and reacting one molecular proportion thereof with two molecular proportions of a sodium alcoholate, the .same type of products will result according to the following equation:

2RONa+X(C1iH2nO) :c-1CnH21iX- wherein R, .X, n, and :1 have the same significance as in the preceding equation.

Many modifications are possible and will suggest themselves to the skilled chemist. For example, an alkylene oxide such as ethyleneoxide or propylene oxide, .or a mixture of oxides, may be reacted with a monohydric alcohol in any well known manner to yield a monoalkyl ether of a polyoxyalkylene glycol. This reaction may be represented for the caseof a single alkylene oxide by the equation 0.1.1 110 V/CH?) (O(IJ.HGH)2 H whereinROH is an aliphatic monohydroxy alcohol, R is H or CH3, and y is a Whole number. This is a well known type of reaction and has been described in U S. Patent 1,633,927. For-the case where a mixture of ethylene oxide and propylene oxide is used, the reaction may be represented by the equation wherein ROH is an aliphatic-monohydroxy alcohol; y and 2 represent the moles of ethyleneoxide and 1,2-propylene oxide respectively; n is both 2 and-3 in a single molecule, the total number of times it has avalue of .2 being equal to y and the total number of times .n has a value of 3 being equal to z; and a: is the total number of such oxyalkylenegroupabeingequalto y+z. Methods I of effecting this reaction with the mixed oxides and the resultant compositions have been described in U. S. Patent.2,425,755.

The resulting monoalkyl ether of a ,polyoxyalkylene glycol may then be reacted with sodium to give the corresponding sodium alcoholate, and this alcoholate reacted (1) with any desired alkyl halide to yield a diether of the polyoxyalkylene glycol, or ('2) with an alkylene dihalide to give a diether of a polyoxyalkylene glycol. These ,reactions are illustrated in the following two equations:

wherein R and R are alkyl; X is halogen, e. 'g., chlorine or bromine; n is 2 or 3, or both; and a: is a whole number.

wherein R, n, and m have the same significance as in Equation 1.

Since, as indicated above, it is possible to prepare the polyethers of this invention by various routes, and from a number of difierent classes of starting materials, the invention should not be limited by the following examples, which are merely intended to illustrate some satisfactory procedures for preparing the few of the materials suitable for employment within the scope of the present invention.

EXAMPLE I A methanol solution of sodium methoxide was prepared by dissolving 2.75 g. (0.119 atom) of sodium in 30 ml. of anhydrous methanol. To this was added 22.0 g. (0.055 mole) of a polyoxyethylene glycol of average molecular weight 400, and the methanol was then removed under reduced pressure at a temperature of 130 degrees C. The resulting sodium salt of the glycol was cooled to degrees C. and 25.5 g. of a commercial grade of dodecyl chloride (molecular weight 213) was added dropwise with stirring over a period of about 30 minutes. The reaction was allowed to continue with stirring at 100-110 degrees C. until a test for alkalinity to phenolphthalein was negative (about 20 hours). The reaction mixture was then filtered free of precipitated sodium chloride, to give the dilauryl ether of the glycol in the form of a clear, straw-colored liquid. It was insoluble but easily dispersible in water.

EXAMPLE II The dilauryl ether of a polyoxyethylene glycol of average molecular'weig-ht 600 was prepared by the procedure of Example I from 2.16 g. of sodium, 22 ml. of anhydrous methanol, 26.8 g. of a polyoxyethylene glycol of average molecular weight 600, and 20.0 g. of the dodecyl chloride described in Example I. The product was a light strawcolored mixture of liquid and solid at room temperature. It was soluble in cold water and insoluble but easily dispersible in hot water.

EXAMPLE III The dicetyl ether of acommercial grade of nonaoxyethylene glycol (average molecular weight of the glycol approximately 400) was prepared according to the .procedure of Example I from 4.83 g. of sodium, 50 ml. of anhydrous methanol. 41.4 g. of the polyoxyethylene glycol, and 64 g. of cetyl bromide. Upon standing at room temperature, the product slowly solidified to a soft grease which was readily dispersible in water.

EXAMPLE IV The disodium salt of a polyoxyethylene glycol of average molecular weight 300 was prepared by mixing 1.54 g. (0.067 atom) of sodium and 11.0 g. (0.036 mole) of the glycol in a flask fitted with a reflux condenser and a mechanical stirrer. A small amount of n-heptane was then added, sufiicient to cover the sodium, and the mixture stirred vigorously while heating to the reflux point of the heptane. After about 8 hours all of the sodium had reacted, whereupon 20.5 g. (0.067 mole) of cetyl bromide was added and the mixture stirred with heating for an additional period of 4 to 8 hours, when a test for alkalinity to phenolphthalein was found to be negative. The resulting dicetyl ether of the glycol, when freed of salt and heptane, was a solid.

EXAIVIPLE V The dicetyl ether of Carbowax 1540, which is a polyoxyethylene glycol of average molecular weight 1540 was prepared according to the procedure of Example I from 2.42 g. (0.105 atom) of sodium, 25 ml. of anhydrous methanol, 77 g. (0.05 mole) of the glycol, and 32 g. (0.105 mole) of cetyl bromide. When cool, the product was a pale yellow wax which was readily dispersible in water.

EXAMPLE VI In a flask equipped with a reflux condenser and a mechanical stirrer was placed 30.0 g. (0.005 mole) of a polyoxyethylene glycol of average molecular weight 6000 (Carbowax 6000) and 0.39 g. (0.01 atom) of potassium. A'protective layer of n-heptane was added on top of the reaction mixture and the mixture stirred at about 100 degrees C. for 8 hours, when all of the potassium had reacted. Then 3.05 g. (0.01 mole) of cetyl bromide was added and the stirring and heating continued until the phenolphthalein alkalinity was gone, which required 10 additional hours. The resulting dicetyl ether of the polyoxyethylene glycol, when freed of salt and heptane, was a solid at room temperature.

EXAMPLE VII The dioctyl ether of a polyoxypropylene glycol of average molecular weight 750 was prepared according to the procedure of Example IV from 1.84 g. (0.08 atom) of sodium, 30.0 g. (0.04 mole) of the glycol, and 11.9 g. (0.08 mole) of n-octyl chloride. The product was a liquid at room temperature.

EXAMPLE VIII The dioctyl ether of a polyoxypropylene glycol of average molecular weight 1200 was prepared according to the procedure of Example IV from 0.92 g. (0.04 atom) of sodium, 24.0 g. (0.02 mole) of the glycol, and 5.95 g. (0.04 mole) of n-octyl chloride. The product was a very viscous liquid at room temperature.

EIQAMIPLE IX The dicetyl ether of a polyoxypropylene glycol of average molecular weight 750 was prepared 8 according to the procedure of Example I from 1.53 g. sodium, 20 ml. of anhydrous methanol, 25 g. (0.033 mole) of the glycol, and 20.36 g. (0.066 mole) of cetyl bromide. When cool, the product was a pale yellow, viscous liquid.

EXAMPLE 2G The dicetyl ether of a polyoxypropylene glycol of average molecular weight 1200 was prepared according to the procedure of Example I from 1.08 g. (0.047 atom) of sodium, 10 ml. of anhydrous methanol, 26.8 g. (0.022 mole) of the glycol, and 14.3 g. (0.047 mole) of cetyl bromide. The product, which was relatively insoluble in water, was a clear liquid at room temperature.

EXAMPLE XI The monobutyl ether of a polyoxypropylene glycol having a total molecular weight of approximately 1400 (for the ether) was converted to the sodium alcoholate form according to the procedure of Example I by the use of 0.41 g. (0.018 atom) of sodium, 15 ml. of anhydrous methanol, and 25 g. (0.018 mole) of the monobutyl ether. After the removal of the methanol and reaction of the alcoholate with 3.8 g. (0.018 mole) of lauryl chloride, the product was obtained as a light straw-colored liquid which was the dialkyl ether wherein one terminal alkyl group was butyl and the other lauryl.

EXAMPLE XIII A solution of sodium methylate was prepared from sodium and anhydrous methanol which contained 0.077 g. of sodium per milliliter. To 8.95 ml. of the sodium methylate solution was added 30 g. (0.030 mole) of the monobutyl ether of a polyoxyalkylene glycol, the polyoxyalkylene chain of which contained ethylene oxide and propylene oxide in a 1:1 ratio, and the total molecular weight (for the butyl ether) of which was approximately 1000. The methanol was then distilled from the reaction mixture, as in Example I, and to the resulting monosodium alcoholate of the monobutyl ether was added 10.07 g. (0.033 mole) of cetyl bromide and the reaction continued as in Example I. The resulting product was the dialkyl ether of the polyoxyalkylene glycol, wherein one terminal alkyl group is butyl and the other is cetyl, and the product has an approximate molecular weight of 1230. At room temperature, the product was a liquid.

The products hereinabove described may be liquids or low-melting wax-like solids, and may be entirely soluble in cold water or only partially soluble. In the latter case, they are relatively easily dispersed in the feed water by means of additional dispersing agents, as described below. All of the products exhibit substantial insolubility in hot water, the phenomenon of decreasing solubility in water with increasing temperature being characteristic of compounds of this class Which contain multiple ether linkages and in which the ratio of ether linkages to carbon is sufliciently great to permit the weak hydrogen bonding effect of the ether oxygen to confer water solubility.

The amounts of an antifoam agent employed in inhibiting the foaming of water in a steam generator will depend upon several factors, among them the percent of solids in the foaming liquid, the nature of the solids, the alkalinity, temperature and pressure, the type and degree of circulation in the steam generator, the rate of steam production, and the amount of foam suppressiondesired. It is,. therefore, impossible to state any rigid rules for estimating the amount of an anti foam which needs to be used. The amounts of the polyethers of this invention which are required are, however, extremely small. For many purposes, amounts of the order of 0.01 grain per gallon to 0.02 grain per gallon in the feed water are sufficient, and under certain-conditions quantities as low as 0.001 grain per gallon in the feed water have proved eifective. In general, it can be said that quantities greater than 0.1 grain per gallon in the feed water would seldom be required.

By way of illustrating the remarkable eifectiveness of the polyethers of this invention, the method of testing their antifoam efficiency in the laboratory will be described and exemplary data given and this will be followed by the results of an actual test made on a full-scale stationary boiler.

In the laboratory, the experimental boiler used was of the type described in the publication Solid matter in boiler water foaming, by Foulk and Brill, which appeared in the periodical Industrial and Engineering Chemistry, volume 27, pages 1430-35. This boiler was fitted with sight glasses on each side of the steam release space so that conditions in the. boiler in a zone several inches above and. below the normal water level were observed While the boiler was operating under pressure. It was also equipped with an automatic water level control Which held the water level within a range of :025 inch.

In the series of experiments described. below, a feed water was usedhaving the following composition, expressed in parts per million, by weight:

Calcium hardness (as CaCOa) 154.0 Magnesium hardness (as CaCOc) 154.0 Alkalinity (methyl orange) (as 09.003)--- 726.0 Sodium chloride (as'NaCl) 85.5 Sodium sulfate (as Na2SO4) 718.0 Tannin extract, dry 34.2

To this feed water was added the antifoam composition of the character and in the quantity specified in the specific experiment, and this water was then gradually concentrated in the test boiler by evaporation at the rate of six gallons per hour at 250 pounds per square inch (p. s. i.) gauge pressure. A continual recording was made of the relative conductivity of the condensate from the boiler, and continual observations were made of the character of the boiling and the amount of foaming as seen through the sight glasses. When the antifoam thus introduced continuously with the feed water was no longer able to overcome the foaming tendencies brought about by the concentration of dissolved solids in the boiler water, the foam height became great enough to cause boiler water to be carried out of the boiler with the steam, and this end-point of the test was determined both by observation through the sight glasses and, particularly, by the abrupt increase in the conductivity of the steam, as shown in the continuous recorder. At this end-point, a sample of the boiler water was withdrawn from the boiler and analyzed, and the effectiveness of the antifoam expressed in terms of the total dissolved solids concentration which I 10 Test I The product of Example'l v' was compounded into a dry, pulverized form in the following way. Three grams were mixed with one gram each of oleic acid and dipropyleneglycol. The resulting liquid mixture was intimately mixed, by grinding, with grams of a dry, pulverized lignin derivative commonly used in boiler water treatment, and made by desulfona-tion and partial depolymerization of sodium lignin sulfonate by treatment with aqueousalkali at high temperatures. This material by itself, or in conjunction with the oleic acid and dipropylene glycol, exhibits an excellent dispersing effect on the dialk-yl ethers of this invention, but exerts no antifoam eiTect per se. The resulting dry-appearing pulverized composition, containing three partsby weight of the product of Example IV', was ad'ded'to" the feed water at a. dosage of 5.7 p. p. m. (parts per million) resulting ina concentration of" the dialkyl ether of 01171 p; p. m. in the feed water. This permitted a total dissolved solids concentration in the boiler of 1824" grains per gallon before carryover occurred.

Test II The product of Example I- was prepared as a stable aqueous dispersion by adding the dialkyl ether towater at the rate of 64.8 mg. of the. ether to l e!) ml; of dispersion. This dispersion was then added to the feedwater soasto give aiconcentration of the dialkylether of 0.0855p. p. m. in the feed water. This permitted a total dissolved solids concentration in the boiler of 1621 grains per gallon before carryover occurred.

One of the difficulties. of using most antifoam materials is that of conveniently introducing them into the Water in small,.controlled amounts so that their maximum effectiveness is utilized. While many of the polyethers employed in accordance with this invention are readily soluble in cold water, others are not completely soluble andmust be rendered readily dispersible for use. Liquids, waxes,- and preformed emulsions are inconvenient to appl-y't'o the feedwaters used by locomotives and other power plants. It is thus a. further object of this. invention to provide the polyethers compounded with other Water treating chemicals in a powdered or briquetted form which can readily and conveniently be. added to water, and which will disperse in the water quickly without excessive agitation or mixing.

The polyethers employed in the practice of this invention can all be incorporated into dry powdered materials such as powdered tannin, sodium ligninsulfonate, the desulfonated lignin described in Test II hereinabove, soda ash, various orthopliosphatesand polyphesphates. Depending somewhat upon the powdered absorbent selected, amounts-of the polyethers of the order of 5- to 10%- of the total composition may bereadily incorporated to give a dry-appearing pulverized product. By the use of suitable binders and other well known techniques, such compositions may also be briquetted.

The resulting dry-appearing products just described are readily and completely dispersible in water when the polyethers themselves are soluble or dispersible. When polyethers are employed which are substantially insoluble in water, such as, for example, the product described in Examples VII, VIII. IX and X, these, too, give dryappearing compositions by the method described if a dispersing agent is used in conjunction with them. In fact. many of the common water treating chemicals of a tannin or lignin nature behave as sufiiciently powerful dispersants to readily disperse the insoluble polyether in the form of a relatively stable aqueous dispersion. Where it is not desired to use the tannins or lignin derivatives in quantity sufficient to act as dispersants for the polyethers, a small amount of soap, such as the alkali metal soaps of oleic acid or tall oil, or a sulfonated oil, may be employed with good results, and the amount of soap or sulfonate thus required is insufficient to interfere with the powerful antifoam effect of the polyethers or to render the boiler compound dirty.

In general, then, the polyethers of this invention may be prepared in the form of dry-appearing pulverized or briquetted compositions which are readily and completely dispersible in water with a minimum of agitation by incorporating them, with or without a dispersant such as soap or sulfonated oil, with various tannins, lignins, or other pulverized chemicals, either alone or in combination.

A few examples will serve to illustrate the preparation of suitable dry-appearing, dispersible compositions.

EXAMPLE A E Per cent Dialkyl ether of Example X 3 Desulfonated lignin derivative described in Test I 9'7 The liquid dialkyl ether was incorporated with the dry, pulverized lignin derivative by adding the liquid to the latter in a mortar. The resultant composition was dry and free flowing and, despite the relative water-insolubility of the dialkyl ether, was readily dispersible in water in concentrations of 3 to or greater.

EXAMPLE B Per cent Dialkyl ether of Example XI 3 Oleic acid 1 Dipropylene glycol 1 Desulfonated lignin derivative described in Test I 95 The first three liquids were combined and the resulting liquid mixture added to the lignin derivative as in Example A. The resultant composition was dry and free flowing and was readily dispersible in water. The residual alkalinity of the lignin derivative served to convert the oleic acid to the soap.

EXAMPLE C Per cent Dialkyl ether of Example III 3 Soda ash 45 Desulfonated lignin derivative described in Test I 50 Sodium septaphosphate 2 can also be used, however, in connection with the generation of steam at much higher pressures and the corresponding temperatures, as, for example, in stationary boilers operating at pressures as high as 1000 to 1500 pounds per square inch. The compositions employed in accordance with the invention are efiective not only in inhibiting foaming but also in conditioning and improving the quality of the steam. For this purpose, they may be used in even smaller amounts than the amounts required for the complete inhibition of foaming and priming.

The polyethers employed in the practice of this invention are desirably used in conjunction with other organic water treating chemicals of the tannin and lignin types in treating many water supplies as will be seen from the following. On Waters high in magnesium salts in which the magnesium in the boiler will generally be in the form of magnesium hydroxide, it is desirable that sufiicient of hydroxylated organic material such as tannins, tannic acid, gallic acid, pyrogallol, catechol, phloroglucinol, etc., be added along with the polyethers. These hydroxylated organic compounds have the ability of nullifying the bad effects of the magnesium hydroxide. Magnesium hydroxide appears to partially selectively adsorb the antifoam material and so take it out of the boiler water so that the full antifoam action cannot be exerted by the antifoam compositions when in this adsorbed state. However, when an organic material such as a tannin is added, magnesium hydroxide appears to lose its ability to interfere with the antifoam action. Inasmuch as most boiler feed waters encountered will have varying amounts of magnesium salts present, it is desirable that such hydroxylated organic compounds be mixed with the polyethers prior to addition to the boiler feed water.

Thus another advantageis evident in preparing and using the pulverized or briquetted compositions hereinabove described containing both the polyether antifoam and the polyhydroxylated organic material of the tannin or lignin-derivative type.

As will be apparent from the foregoing description, the compounds employed in accordance with the invention do not all give the same results and from that standpoint are not necessarily equivalents. Some of these polyether compositions, especially those of the type referred to in Test I, are truly remarkable in their foam inhibiting properties even when compared with the best of the antifoam compositions which have been previously used commercially.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a foam inhibiting quantity of a non-ionic diether of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, the said diether is insoluble in said water under the conditions of said steam generation and the average molecular weight of said diether is at least 500.

2. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a Water therein containing an amount of total solids tending to produce foaming and priming a foam inhibiting quantity of a non-ionic diether of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, the said compound is insoluble in said water under the conditions of said steam generation, the average molecular weight of said diether is at least 500, and said quantity is within the range of 0.001 grain to 0.1 grain per gallon of water.

3. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a foam inhibiting quantity of a non-ionic diether of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, the said compound is insoluble in said water under the conditions of said steam generation, the average molecular weight of said diether is at least 500, and said superatmospheric pressure conditions are within the range of 100 to 1500 pounds per square inch and the corresponding temperatures.

4. A process of minimizing the production of foam in and the priming of steam generators operating under superatmosp-heric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a foam inhibiting quantity of a non-ionic diether of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, the said compound is insoluble in said water under the conditions of said steam generation, the average molecular weight of said diether i at least 500, and said superatmospheric pressure conditions are Within the range of 100 to 300 pounds per square inch and the corresponding temperatures.

5. A process of minimizing foaming in steam generators which comprises incorporating with water therein a dialkyl ether of a polyoxyalkylene glycol wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, said dialkyl ether being from the group consisting of dialkyl ethers of polyoxyethylene glycols in which each terminal alkyl group is of substantially the same size and contains at least 12 carbon atoms and the molecular weight of the whole compound is greater than 600, dialkyl ethers of polyoxypropylene glycols in which the terminal alkyl groups are substantially of the same size, contain at least 8 carbon atoms and the molecular weight is greater than 500, dialkyl ethers wherein both ethylene and propylene groups occur in the polyoxyalkylene chain, the terminal alkyl groups are of substantially the same size, each terminal alkyl group contains at least 8 carbon atoms and the molecular weight of the whole compound is greater than 600 and dialkyl ethers of said polyoxyalkylene glycols wherein the terminal alkyl groups differ widely in the number of carbon atoms one terminal alkyl group containing at least 12 carbon atoms and the other containing 1 to 6 carbon atoms and the total molecular weight of the whole compound is at least 1500, said compounds being insoluble in said water under the conditions of said steam generation and said quantity being suflicient substantially to inhibit said foaming.

6. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing in said water a quantity of a dialkyl ether of a polyoxyethylene glycol in which each terminal alkyl group is of substantially the same size and contains at least 12 carbon atoms and the molecular Weight of the whole compound is greater than 600, said dialkyl ether being insoluble in said water under the conditions of said steam generation and said quantity being sufiicient substantially to inhibit said foaming, and heating the resultant aqueous dispersion to the boiling point.

'7. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing in said water a quantity of a dialkyl ether of a polyoxypropylene glycol in which the terminal alkyl groups are substantially the same size and contain at least 8 carbon atoms and the molecular weight of the whole compound is greater than 500, said dialkyl ether being insoluble in said water under the conditions of said steam generation and said quantity being sufficient substantially to inhibit said foaming, and heating the resultant aqueous dispersion to the boiling point.

8. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing in said water a quantity of a dialkyl ether of a polyoxyalkylene glycol wherein both ethylene and propylene groups occur in the polyoxyalkylene chain, the terminal alkyl groups are of substantially the same size, each terminal alkyl group contains at least 8 carbon atoms and the molecular weight of the whole compound is greater than 600, said dialkyl ether being insoluble in said water under the conditions of said steam generation and said quantity being sufficient substantially to inhibit said foaming, and heating the resultant aqueous dispersion to the boiling point.

9. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing in said water a quantity of a dialkyl ether of a polyoxyalkylene glycol wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, the terminal alkyl groups differ widely in the number of carbon atoms, one terminal alkyl group containing at least 12 carbon atoms and the other containing 1 to 6 carbon atoms and the total molecular weight of the whole compound is at least 1500, said dialkyl other being insoluble in said water under the conditions of said steam generation and said quantity being sufiicient substantially to inhibit said foaming, and heating the resultant aqueous dispersion to the boiling point.

ARTHUR L. JACOBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,425,755 Roberts et a1 Aug. 19, 1947 2,442,768 Gunderson June 8, 1948 2,520,611 Roberts et al Aug. 29, 1950 

1. A PROCESS OF MINIMIZING THE PRODUCTION OF FOAM IN AND THE PRIMING OF STEAM GENERATORS OPERATING UNDER SUPERATMOSPHERIC PRESSURE CONDITIONS WHICH COMPRISES INCORPORATING WITH A WATER THEREIN CONTAINING AN AMOUNT OF TOTAL SOLIDS TENDING TO PRODUCE FOAMING AND PRIMING A FOAM INHIBITING QUANTITY OF A NON-IONIC DIETHER OF A POLYOXYALKYLENE GLYCOL, WHEREIN THE ALKYLENE RADICALS ARE SELECTED FROM THE GROUP CONSISTING OF ETHYLENE, PROPYLENE AND MIXTURES THEREOF, THE SAID DIETHER IS INSOLUBLE IN SAID WATER UNDER THE CONDITIONS OF SAID STEAM GENERATION AND THE AVERAGE MOLECULAR WEIGHT OF SAID DIETHER IS AT LEAST
 500. 